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--- title: Troubleshoot File Compression titleSuffix: Azure Front Door description: Learn how to troubleshoot issues with file compression in Azure Front Door. This article covers several possible causes. author: halkazwini ms.author: halkazwini ms.service: azure-frontdoor ms.topic: how-to ms.date: 11/18/2024 --- # Troubleshoot Azure Front Door file compression **Applies to:** :heavy_check_mark: Front Door Standard :heavy_check_mark: Front Door Premium This article helps you troubleshoot file compression issues in Azure Front Door. ## Symptom Compression is enabled for your route, but files are being returned uncompressed. > [!TIP] > To check if your files are compressed, use a tool like [Fiddler](https://www.telerik.com/fiddler) or your browser's [developer tools](/microsoft-edge/devtools-guide-chromium/overview). Look for the `Content-Encoding` header in the HTTP response. If it has a value of **gzip**, **bzip2**, or **deflate**, your content is compressed. > >  ## Cause Possible causes include: * The content isn't eligible for compression. * Compression isn't enabled for the file type. * The HTTP request lacks a valid compression type header. * The origin is sending chunked content. ## Troubleshooting steps > [!TIP] > Azure Front Door configuration changes can take up to 10 minutes to propagate. If this is your first time setting up compression, wait 1-2 hours to ensure settings have propagated to the POPs. ### Verify the request Use your browser's **[developer tools](/microsoft-edge/devtools-guide-chromium/overview)** to check the requests: * Ensure the request is sent to `<endpointname>.z01.azurefd.net`, not your origin. * Ensure the request includes an **Accept-Encoding** header with **gzip**, **deflate**, or **bzip2**.  ### Verify compression settings In the [Azure portal](https://portal.azure.com), navigate to your endpoint and select **Configure** in the Routes panel. Ensure compression is **enabled**.  ### Check the request at the origin server for a **Via** header The **Via** header indicates a proxy server. By default, Microsoft IIS servers don't compress responses with a **Via** header. To override this: * **IIS 6**: Set HcNoCompressionForProxies="FALSE" in the IIS Metabase properties. See [IIS 6 Compression](/previous-versions/iis/6.0-sdk/ms525390(v=vs.90)). * **IIS 7 and up**: Set **noCompressionForHttp10** and **noCompressionForProxies** to *False* in the server configuration. See [HTTP Compression](https://www.iis.net/configreference/system.webserver/httpcompression). ## Next steps For more information, see [Azure Front Door FAQ](../front-door-faq.yml).